Edited by: Joe Hing kwok Chu
There is a new age culture to drink raw vegetable juice. Some vegetable are high in oxalic acid which can damage kidneys from the forming of kidney stones.
People who have high blood pressure, or prone to kidney stones or diabetes should avoid food high in oxalic acid.
Some vegetables are high in potassium.
Some people with kidney yang deficient already retaining too much potassium. Too much potassium can be toxic to the heart.
Juicing those vegetables can retain too much potassium or oxalic acid.
Boiling them can remove some potassium salt or oxalic acid or oxalate by dissolving the chemicals in water. Discarding the liquid after boiling can cut down the the intake.
Some vegetables can toxic when they are raw. For examples:
(1) Soy and soy milk:
Raw soybeans contain saponin, which is toxic. After boiling saponin is destroyed. Consuming raw soy milk can cause food poisoning.
Beware that when soy milk is heated to about 80 ℃, the saponin will expand and create bubbles, creating a illusion that it is boiling, a "false boiling" phenomenon. At this temperature the soy milk toxic saponin is not completely destroyed. Drinking it can cause poisoning, usually after half hour to 1 hours the symptoms of gastroenteritis will occur.
Detoxifying soy and soy milk:
Boil the soy milk till the bubbles are dissipated then boil further for about 10 more minutes. Usually when the soy beans are cooked till soft, it is safe.
(2) Green beans:
Raw green beans contain saponin which is toxic. It can strongly stimulate the digestive tract. Green beans also contain phytohemagglutinin (a lectin) , with blood clotting effect.
Furthermore beans also contain nitrite and trypsin and can stimulate the stomach, and can also cause food poisoning, gastroenteritis symptoms.
Detoxifying green beans:
Usually cooking until soft to eat, it will be safe.
(3) Cassava (木薯):
The cassava roots and leaves contain two cyanogenic glucosides:
linamarin
lotaustralin
After consuming the cassava roots, the cyanogenic glucosides after hydrolizing by the stomach acid they become the free form of hydrogen cyanide and become highly toxic.
The amounts of these potentially toxic compounds vary considerably, according to growing conditions and varieties. "Sweet" varieties (Manihot esculenta Crantz) usually have such small amounts as to be innocuous, whereas bitter varieties (Manihot utilissima Pohl.) have sufficiently high levels to require processing to remove most of the toxins.
Detoxifying cassava
Boiling and drying are sufficient to make low-cyanogen variety (Manihot esculenta Crantz) safe for consumption. For the bitter variety (Manihot utilissima Pohl.) of higher toxicity more rigorous procedures such as grating, fermenting, and sun-drying, are necessary to effectively to remove the cyanogens.
Fava beans (蠶豆，faba beans, broad beans)
Fava beans contain vetch alkali glycosides. Consuming this substance, can cause acute hemolytic anemia (favism). Eating fava beans during spring and summer, if not cooked properly, can cause poisoning phenomenon. Usually after eating raw fava beans symptoms can occur in 4 to 24 hours.
Detoxifying fava beans: cooking will remove the toxin.
Jin zhen cai 金針菜 (flowers of easter lily plant)
Huang hua cai 黃花菜 is also known as jin zhen cai 金針菜. It is the flowers of easter lily plant. It is one of the favorite Chinese dishes. But the raw lilies contain colchicine. After consuming raw lilies, the colchicine will be oxidized in the body tissues, generating two-colchicine. The two-Colchicine is a highly toxic substance that can poison the human gastrointestinal tract, urinary system, a serious threat to health. An adult, if an ingestion of 50 to 100 grams of fresh lily can cause poisoning.
Although colchicine poisoning is relatively uncommon, it is imperative to recognize its features as it is associated with a high mortality rate when missed.[1]
[1] Clin Toxicol (Phila). 2010 Jun;48(5):407-14. doi: 10.3109/15563650.2010.495348.